Available at MTV's website, the MTV On Demand (MTV OD) service features full-length episodes of current and archived shows, including The Real World, The Hills and 16 and Pregnant.
The online portal also offers exclusive MTV content, such as preview episodes and behind-the-scenes footage, along with Facebook links for sharing content.
UK users will need to pay either £1 for a day's access, or £2 for a week-long pass to view as much programming as they want. Payments can be made via SMS or PayPal.
MTV Networks International senior vice president Philip O'Ferrall said that the new MTV generation is "connected and driven by search and social media recommendation".
O'Ferrall added: "We are launching MTV OD in response to the tremendous demand for full-length content on our websites. MTV OD will ensure that the content our fans want is at their fingertips.
"Viewers can choose to watch current MTV shows or to browse our archive, allowing them to enjoy classic episodes and even discover iconic shows they may not have previously heard of.
"MTV OD both expands our 360 vision for all of our linear shows and increases our digital footprint, enabling us to make our shows more available to fans than they have ever been before."
The MTV OD portal features full media player functionality, including variable bandwidth streaming to ensure maximum image quality and video playback.